A problem found in the field of dishwashing is the removal of coloured stains from dishware/tableware, in particular from plastic substrates which have been in contact with coloured foods. In addition, the coloured material when removed or partially removed from the stained substrate can deposit on the plastic parts of an automatic dishwashing machine.
Different solutions have been proposed to tackle the removal and deposition of coloured stains from plastic in a machine dishwashing method. WO 03/095598 relates to a process for removing coloured stains from plastic by treating the substrate in an ADW machine with an aqueous liquor having a peroxide value of 0.05 to 40 (peroxide components include terpenes). In WO 03/095599 the coloured stains from plastic are removed by treating the substrate with a composition comprising 3-phenyl-2-propenal and/or 3,7-dimethyl-2,6-octadien-1-al. WO 03/095602 presents another alternative process for removing coloured stains from plastic by treating the substrate with an aqueous composition comprising a hydrophobic component having a density in the range of 0.06 to 1 gram/cm3. Hydrophobic components include hydrocarbon oil and edible oil. Paraffin oil is the preferred hydrophobic component.
Diacyl and/or tetraacyl peroxide bleaching species may be used to inhibit the transfer of coloured/bleachable soils when employed in a laundry (WO 93/07086) or dishwashing (WO 95/19132) method. Such species are however intrinsically unstable above their melting points and are liable to self-accelerating thermal decomposition. To provide storage stability '086 and '132 propose the incorporation of the diacyl and tetraacyl bleaching species as “guest” molecules in “host-guest complexes” in which the molecules of the bleaching species are individually separated from each other by their inclusion in the host receptor sites. The hosts may for example be inorganic or organic crystals having relatively open structures which provide sites that may be occupied by guest molecules, thus forming the host-guest complexes. Examples of suitable hosts include certain clathrates or inclusion compounds, including the urea clathrates and the cyclodextrins, particularly the beta-cyclodextrins. The hosts are most preferably water soluble, to enable effective release and dispersion of the bleaching species on introduction of the host-bleaching species complexes into an aqueous media, such as a wash solution. Urea clathrates of diacyl and tetraacyl bleaching species have been disclosed in both WO 93/07086 and WO 95/19132.
There is the need of less complex processes for introducing diacyl and/or tetraacyl peroxide bleaching species into detergents.
Some bleaches, in particular some acyl peroxides, are commercially available in the form of flakes and as such they could give rise to segregation issues if they are included in granular detergent compositions. This could result in a high variability of the bleach in the product and affect product performance.
Some acyl peroxides have a waxy consistency and they tend to be sticky that makes them undesirable for use in solid detergent compositions because they can give rise to agglomeration issues impairing on the flowability and dissolution of the detergent.
An added complication when dealing with bleaches, in particular some acyl peroxides, is that they can degrade thermally at low temperatures, thereby making their handling and processing complex.
The object of this invention is to provide bleach, in particular acyl peroxide bleach, in a form suitable for introduction in a detergent, in particular a granular detergent. In addition, the bleach should have good stability.